Ultra-short echo-time magnetic resonance imaging distinguishes ischemia/reperfusion injury from acute rejection in a mouse lung transplantation model.

To investigate whether lung tissue characterization by ultra-short echo-time (UTE) magnetic resonance imaging (MRI) allows ischemia/reperfusion injury to be distinguished from acute rejection in a mouse lung transplantation model. After orthotopic lung transplantation with 6 mice receiving syngeneic (C57Bl/6) lung transplants and 6 mice receiving allogeneic (BALB/c) transplants, they underwent postoperative imaging using three-dimensional UTE-MRI (echo times TE = 50-5000 μs) and conventional T2-weighted fast spin-echo imaging. Quantitative T2* values of lung transplant parenchyma and spin density (SD) were compared by region-of-interest analysis. All samples underwent histological and immunohistochemical workup. In the allogeneic group, alveolar infiltration resulting from acute organ rejection was visualized in the UTE sequences. This was reflected by the quantitative measurements of SD and T2* values with higher values in the allogeneic group compared with the syngeneic group and nontransplanted lung at the first time point (24 h postoperative: Tx allogeneic group SD: 2133.9 ± 516; Tx syngeneic group SD: 1648.61 ± 271; P = 0.004; Tx allogeneic group T2*: 1710.16 ± 644 μs, Tx syngeneic group T2*: 577.16 ± 263 μs; P = <0.001). Changes caused by acute rejection after lung transplantation can be visualized and characterized using a UTE sequence due to different relaxation properties compared with both syngeneic lung transplants and normal lung tissue.